Peptide Tyrosine Tyrosine (PYY3-36) is an endogenous humoral peptide that has been shown to increase postprandially in proportion to the calorie content of meals. PYY3-36 has also been shown to inhibit food intake in animals and humans, thus, the understanding of its function is important both scientifically and clinically. The long-term goal of the proposed research is to understand the role of PYY3-36 in the intricate balance of energy homeostasis. There are several aspects of PYY3-36 action that are of interest, such as the anatomical site of its action and involvement of the melanocortin system in the generation of physiological output response to postprandial secretion of the peptide. Furthermore, we would like to compare the action PYY3-36 to PYY1-36 and also elucidate the physiological role of PYY3-36 as a peripheral feedback signal of the satiety response. Finally, we are interested in determining whether PYY3-36 is acting as a short or long-term peripheral signal to the CNS. [unreadable] [unreadable]